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Abstract:

A fundamental wavelength light generating unit generates light of a
fundamental wavelength in accordance with an output wavelength
instruction signal. An optical amplifier unit amplifies the light of the
fundamental wavelength. A wavelength converting part includes nonlinear
optical crystals that each perform wavelength conversion and temperature
regulators that each regulate the temperature of the corresponding
nonlinear optical crystal, wherein the wavelength converting part
converts the light amplified by the optical amplifier unit to light of
the wavelength indicated by the output wavelength instruction signal. A
storage unit stores correspondence information that indicates a
correspondence relationship between the wavelength of the output light
and the temperature of each of the nonlinear optical crystals based on
the corresponding wavelength. A control unit controls each of the
temperature regulators such that the temperature of the corresponding
nonlinear optical crystal reaches the temperature to be set in accordance
with the output wavelength instruction signal.

Claims:

1. A laser apparatus that outputs wavelength tunable output light,
comprising: a fundamental wavelength light generating unit, which
generates light of the fundamental wavelength in accordance with an
output wavelength instruction signal that specifies the wavelength of the
output light; an optical amplifier unit, which amplifies the light of the
fundamental wavelength; a wavelength converting part that comprises a
plurality of nonlinear optical crystals, each nonlinear optical crystal
performing wavelength conversion, and a plurality of temperature
regulators, each temperature regulator regulating the temperature of the
corresponding nonlinear optical crystal, wherein the wavelength
converting part converts the light amplified by the optical amplifier
unit to light of the wavelength indicated by the output wavelength
instruction signal; a storage unit, which stores correspondence
information that indicates a correspondence relationship between the
wavelength of the output light and the temperature of each of the
nonlinear optical crystals to be set in accordance with the corresponding
wavelength; and a control unit that controls each of the temperature
regulators such that the temperature of the corresponding nonlinear
optical crystal reaches the temperature to be set as determined by the
correspondence information in accordance with the output wavelength
instruction signal.

3. A laser apparatus according to claim 2, wherein the wavelength tunable
laser light source comprises a laser light source temperature regulator
and generates light of an oscillation wavelength corresponding to the
temperature regulated by the laser light source temperature regulator as
the light of the fundamental wavelength; the storage unit stores
correspondence information that indicates the correspondence relationship
between the wavelength of the output light and the temperature of the
wavelength tunable laser light source to be set in accordance with that
wavelength; and the control unit controls the laser light source
temperature regulator such that the temperature of the wavelength tunable
laser light source reaches the temperature to be set as determined by the
correspondence information in accordance with the output wavelength
instruction signal.

4. A light therapy apparatus, comprising: a laser apparatus according to
claim 1; and a radiation optical system, which guides and radiates output
light output from the laser apparatus to a therapy region.

5. An exposure apparatus, which transfers a pattern of a mask to a
photosensitive object, comprising: a laser apparatus according to claim
1; an illumination optical system, which radiates output light output
from the laser apparatus to the mask; and a projection optical system,
which projects light from the mask to the photosensitive object.

6. A device fabricating method, which includes a lithographic process,
comprising the step of: using the exposure apparatus according to claim 5
to transfer, in the lithographic process, the pattern of the mask to the
photosensitive object.

7. An object inspection apparatus, comprising: a laser apparatus
according to claim 1; a support part, which supports an object to be
inspected; a detector, which detects a projected image of the object to
be inspected; an illumination optical system, which radiates output light
output from the laser apparatus to the object to be inspected; and a
projection optical system, which projects light from the object to be
inspected to the detector.

8. A light therapy apparatus, comprising: a laser apparatus according to
claim 2; and a radiation optical system, which guides and radiates output
light output from the laser apparatus to a therapy region.

9. A light therapy apparatus, comprising: a laser apparatus according to
claim 3; and a radiation optical system, which guides and radiates output
light output from the laser apparatus to a therapy region.

10. An exposure apparatus, which transfers a pattern of a mask to a
photosensitive object, comprising: a laser apparatus according to claim
2; an illumination optical system, which radiates output light output
from the laser apparatus to the mask; and a projection optical system,
which projects light from the mask to the photosensitive object.

11. An exposure apparatus, which transfers a pattern of a mask to a
photosensitive object, comprising: a laser apparatus according to claim
3; an illumination optical system, which radiates output light output
from the laser apparatus to the mask; and a projection optical system,
which projects light from the mask to the photosensitive object.

12. An object inspection apparatus, comprising: a laser apparatus
according to claim 2; a support part, which supports an object to be
inspected; a detector, which detects a projected image of the object to
be inspected; an illumination optical system, which radiates output light
output from the laser apparatus to the object to be inspected; and a
projection optical system, which projects light from the object to be
inspected to the detector.

13. An object inspection apparatus, comprising: a laser apparatus
according to claim 3; a support part, which supports an object to be
inspected; a detector, which detects a projected image of the object to
be inspected; an illumination optical system, which radiates output light
output from the laser apparatus to the object to be inspected; and a
projection optical system, which projects light from the object to be
inspected to the detector.

Description:

RELATED ART

[0001] The present invention relates to a laser apparatus and to a light
therapy apparatus, an exposure apparatus, a device manufacturing method,
and an object inspection apparatus that uses such a laser apparatus.

RELATED ART

[0002] Patent Document 1 below discloses a laser apparatus that comprises:
a laser light generating unit, which generates laser light of a single
wavelength that falls within the wavelength range of the infrared region
to the visible region; an optical amplifier unit, which comprises an
optical fiber amplifier that amplifies the laser light generated by the
laser light generating unit; a plurality of nonlinear optical crystals,
wherein each of the nonlinear optical crystals performs wavelength
conversion of the laser light amplified by the optical amplifier unit;
and a wavelength converting part, which comprises a plurality of
temperature control apparatuses, wherein the temperature control
apparatuses control the temperatures of the nonlinear optical crystals in
order to adjust their phase matching angles during wavelength conversion;
furthermore, the laser apparatus generates ultraviolet light from the
wavelength converting part. Controlling the temperatures via the
temperature control apparatuses adjusts the phase matching angles of all
of the nonlinear crystals, which makes it possible to increase conversion
efficiency using simple control.

[0003] In addition, page 19 through page 21 in Patent Document 1 recites
that a DFB semiconductor laser is used as the laser light generating
unit, and that either the oscillation wavelength may be stabilized and
kept at a constant wavelength by controlling the temperature of the DFB
semiconductor laser or the output wavelength can be adjusted by actively
varying that oscillation wavelength.

PRIOR ART LITERATURE

Patent Documents

[0004] Patent Document 1: Reissued Patent No. WO2001/020397

OVERVIEW OF THE INVENTION

Problems Solved by the Invention

[0005] Nevertheless, in a laser apparatus of the type discussed above,
even if a DFB semiconductor laser is used as the laser light generating
unit and the output wavelength can be adjusted by actively varying the
oscillation wavelength, which is achieved by controlling the temperature
of the DFB semiconductor laser, the tuning range of the output wavelength
of the laser apparatus is relatively narrow and achieving adequate
wavelength tuning performance is difficult, both of which are problems.

[0006] The present invention considers such circumstances, and it is an
object of the present invention to provide a laser apparatus that can
expand the tunable wavelength range of output light, and to provide a
light therapy apparatus, an exposure apparatus, a device manufacturing
method, and an object inspection apparatus that uses such a laser
apparatus.

Means for Solving the Problems

[0007] Means for solving the aforementioned problems are presented in the
aspects below. A laser apparatus according to a first aspect of the
invention is a laser apparatus that outputs tunable wavelength output
light and that comprises: (i) a fundamental wavelength light generating
unit, which generates light of a fundamental wavelength in accordance
with an output wavelength instruction signal that specifies the
wavelength of the output light; (ii) an optical amplifier unit, which
amplifies the light of the fundamental wavelength; (iii) a wavelength
converting part that comprises a plurality of nonlinear optical crystals,
each nonlinear optical crystal performing wavelength conversion, and a
plurality of temperature regulators, each temperature regulator
regulating the temperature of the corresponding nonlinear optical
crystal, wherein the wavelength converting part converts the light
amplified by the optical amplifier unit to light of the wavelength
indicated by the output wavelength instruction signal; (iv) a storage
unit, which stores correspondence information that indicates a
correspondence relationship between the wavelength of the output light
and the temperature of each of the nonlinear optical crystals to be set
in accordance with the corresponding wavelength; and (v) a control unit
that controls each of the temperature regulators such that the
temperature of the corresponding nonlinear optical crystal reaches the
temperature to be set as determined by the correspondence information in
accordance with the output wavelength instruction signal.

[0008] A light therapy apparatus according to a second aspect of the
invention comprises: a laser apparatus according to the first aspect of
the invention; and a radiation optical system, which guides and radiates
output light output from the laser apparatus to a therapy region.

[0009] An exposure apparatus according to a third aspect of the invention
is an exposure apparatus, which transfers a pattern of a mask to a
photosensitive object, that comprises: a laser apparatus according to the
first aspect of the invention; an illumination optical system, which
radiates output light output from the laser apparatus to the mask; and a
projection optical system, which projects light from the mask to the
photosensitive object.

[0010] A device fabricating method according to a fourth aspect of the
invention is a device fabricating method, which includes a lithographic
process, that comprises the step of: using the exposure apparatus
according to the third aspect of the invention to transfer, in the
lithographic process, the pattern of the mask to the photosensitive
object.

[0011] An object inspection apparatus according to a fifth aspect of the
invention comprises: a laser apparatus according to the first aspect of
the invention; a support part, which supports an object to be inspected;
a detector, which detects a projected image of the object to be
inspected; an illumination optical system, which radiates output light
output from the laser apparatus to the object to be inspected; and a
projection optical system, which projects light from the object to be
inspected to the detector.

EFFECTS OF THE INVENTION

[0012] The present invention provides a laser apparatus that can expand
the tunable wavelength range of output light, and provides a light
therapy apparatus, an exposure apparatus, a device manufacturing method,
and an object inspection apparatus that uses such a laser apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic block diagram that shows a laser apparatus
according to a first embodiment of the present invention.

[0014]FIG. 2 is a diagram that shows a fundamental wavelength light
generating unit, an optical amplifier unit, and a wavelength converting
part, each of which is shown in FIG. 1.

[0015]FIG. 3 is a diagram that shows the characteristics of a nonlinear
optical crystal.

[0016]FIG. 4 is a schematic block diagram that shows a light therapy
apparatus according to a second embodiment of the present invention.

[0017]FIG. 5 is a schematic block diagram that shows a radiation optical
system and an observation optical system that constitute the light
therapy apparatus shown in FIG. 4.

[0018]FIG. 6 is a schematic block diagram that schematically shows an
exposure apparatus according to a third embodiment of the present
invention.

[0019]FIG. 7 is a schematic block diagram that shows a mask defect
inspection apparatus according to a fourth embodiment of the present
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A laser apparatus, a light therapy apparatus, an exposure
apparatus, a device manufacturing method, and an object inspection
apparatus according to the present invention will now be explained,
referencing the drawings.

First Embodiment

[0021]FIG. 1 is a schematic block diagram that shows a laser apparatus 1
according to a first embodiment of the present invention. FIG. 2 is a
diagram that shows a fundamental wavelength light generating unit 10, an
optical amplifier unit 20, and a wavelength converting part 30, each of
which is shown in FIG. 1. FIG. 1 shows only those constituent elements of
the fundamental wavelength light generating unit 10 and the wavelength
converting part 30 that are related to temperature control. Moreover, in
FIG. 2, among the constituent elements of the fundamental wavelength
light generating unit 10 and the wavelength converting part 30,
temperature regulators 31a, 32a, 34a, 37a, 39a, 40a and temperature
detectors 31b, 32b, 34b, 37b, 39b, 40b are omitted.

[0022] The laser apparatus 1 according to the present embodiment outputs
output light of a tunable wavelength and, as shown in FIG. 1, comprises:
the fundamental wavelength light generating unit 10; the optical
amplifier unit 20; the wavelength converting part 30; a main control unit
50; a correspondence information storage unit 60, which comprises
nonvolatile memory and the like; and a temperature control unit 70.

[0023] The fundamental wavelength light generating unit 10 is configured
such that light of the fundamental wavelength is generated in accordance
with an output wavelength instruction signal, which specifies the
wavelength of the output light of the laser apparatus 1. In the present
embodiment, the main control unit 50 receives the output wavelength
instruction signal from a source external to the laser apparatus 1, but
the present invention is not limited thereto. For example, if a user, an
installer, or the like specifies the wavelength of the output light of
the laser apparatus 1, then the output wavelength instruction signal may
be issued by, for example, a potentiometer that is installed in the laser
apparatus 1.

[0024] In the present embodiment, as shown in FIG. 1 and FIG. 2, the
fundamental wavelength light generating unit 10 is configured as a
temperature controlled tunable laser light source and comprises: a DFB
(distributed feedback) semiconductor laser 11; a laser light source
temperature regulator 11a, such as a Peltier device, that regulates the
temperature of the DFB semiconductor laser 11; a temperature detector
11b, such as a thermistor, that detects the temperature of the DFB
semiconductor laser 11; and an electrical pulse generator 12.

[0025] An InGaAsP DFB semiconductor laser, for example, that can tune its
oscillation wavelength within a prescribed range that includes 1.547
μm is used as the DFB semiconductor laser 11. The electrical pulse
generator 12 is a driver that controls the operation of the DFB
semiconductor laser 11 and, for example, pulses a drive signal with a
pulse width of approximately 1 ns and a repetition frequency f equal to
several tens to several hundreds of kilohertz and supplies such to the
DFB semiconductor laser 11. Thereby, the DFB semiconductor laser 11
outputs to the optical amplifier unit 20 pulsed light of the fundamental
wavelength (i.e., light of the fundamental wave) with a peak power of
approximately 10 mW.

[0026] Correspondence information that indicates the correspondence
relationship between the wavelength of the output light of the laser
apparatus 1 and the temperature of the DFB semiconductor laser 11 needed
to output the output light at that wavelength from the laser apparatus 1
(hereinbelow, called the "output wavelength and laser temperature
correspondence relationship") is stored in advance in the correspondence
information storage unit 60. In the present embodiment, as discussed
below, the wavelength converting part 30 outputs light of a wavelength
that is 1/8 the wavelength of the fundamental wave output by the
fundamental wavelength light generating unit 10 as the output light of
the laser apparatus 1. Accordingly, the wavelength of the fundamental
wave output by the fundamental wavelength light generating unit 10 must
be eight times the wavelength of the output light of the laser apparatus
1. As is well known in the art, the wavelength of the output light of the
DFB semiconductor laser 11 can be adjusted by varying the temperature of
the DFB semiconductor laser 11. Accordingly, in the present embodiment,
the correspondence information that indicates the correspondence
relationship between the wavelength of the output light of the laser
apparatus 1 and the temperature of the DFB semiconductor laser 11 when
the DFB semiconductor laser 11 generates light with a wavelength that is
eight times the wavelength of the output light of the laser apparatus 1
is stored in the correspondence information storage unit 60 as the output
wavelength and laser temperature correspondence relationship. There are
individual differences in the correspondence relationship between the
temperature of the DFB semiconductor laser 11 and the wavelength of the
output light of the DFB semiconductor laser 11. Consequently, it is
preferable to obtain the output wavelength and laser temperature
correspondence relationship, in advance, based on the temperature
detected by the temperature detector 11b while the temperature regulation
state of the temperature regulator 11a is successively changed and on the
result of actually measuring the wavelength of the output light of the
DFB semiconductor laser 11. The correspondence information that indicates
the output wavelength and laser temperature correspondence relationship
may be stored in the correspondence information storage unit 60 in the
form of an approximation expression or a lookup table.

[0027] When controlling the temperature of the DFB semiconductor laser 11,
the main control unit 50 references the correspondence information stored
in the correspondence information storage unit 60 based on the output
wavelength instruction signal in order to acquire the temperature of the
DFB semiconductor laser 11 to be set in accordance with the output
wavelength indicated by the output wavelength instruction signal, and
supplies that temperature to the temperature control unit 70 as the
target temperature of the DFB semiconductor laser 11. The temperature
control unit 70 performs feedback control such that the temperature of
the DFB semiconductor laser 11 reaches the target temperature by
supplying an adjustment signal to the temperature regulator 11a in
accordance with the target temperature and a detection signal output from
the temperature detector 11b.

[0028] Based on this temperature control, the DFB semiconductor laser 11
(and, in turn, the fundamental wavelength light generating unit 10)
generates light of the fundamental wavelength in accordance with the
output wavelength instruction signal. Thus, in the present embodiment,
the fundamental wavelength light generating unit 10 is configured as a
temperature controlled wavelength tunable laser light source, but it may
be configured as a wavelength tunable laser light source of some other
type. For example, the oscillation wavelength of the laser light source
may be varied by disposing inside a resonator of the laser light source
an optical system for setting the oscillation wavelength and varying the
optical path length of a prescribed portion inside that optical system.

[0029] As shown in FIG. 2, the optical amplifier unit 20 comprises: a
coupler 21, which splits the light of the fundamental wave generated by
the fundamental wavelength light generating unit 10 into three parts; a
first EDFA 22, which serves as an optical amplifier that amplifies one of
the lights resulting from the split; a retarder 23, which retards another
one of the lights resulting from the split; a second EDFA 24, which
serves as an optical amplifier that amplifies the light retarded by the
retarder 23; a retarder 25, which retards the one remaining light
resulting from the split; and a third EDFA 26, which serves as an optical
amplifier that amplifies the light retarded by the retarder 25.

[0030] Next, the wavelength converting part 30 will be explained. As shown
in FIG. 1 and FIG. 2, the wavelength converting part 30 comprises: a
plurality of nonlinear optical crystals 31, 32, 34, 37, 39, 40, wherein
each of the nonlinear optical crystals performs wavelength conversion;
and the plurality of temperature regulators 31a, 32a, 34a, 37a, 39a, 40a,
wherein each of the temperature regulators is, for example, a heater that
regulates the temperature of the corresponding nonlinear optical crystal;
furthermore, the light amplified by the optical amplifier unit 20 is
converted to light of the wavelength indicated by the output wavelength
instruction signal. The temperature detectors 31b, 32b, 34b, 37b, 39b,
40b, which are thermistors, are provided to and detect the temperatures
of the nonlinear optical crystals 31, 32, 34, 37, 39, 40, respectively.

[0031] In the present embodiment, a PPLN crystal that constitutes a second
harmonic wave generating optical element is used as the nonlinear optical
crystal 31. A PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like
may be used as the nonlinear optical crystal 31. An LBO crystal that
constitutes a third harmonic wave generating optical element is used as
the nonlinear optical crystal 32. An LBO crystal that constitutes a fifth
harmonic wave generating optical element is used as the nonlinear optical
crystal 34. A BBO crystal or a CBO crystal may be used as the nonlinear
optical crystal 34. A PPLN crystal that constitutes a second harmonic
wave generating optical element is used as the nonlinear optical crystal
37. A PPKTP crystal, a PPSLT crystal, an LBO crystal, or the like may be
used as the nonlinear optical crystal 37. A CLBO crystal that constitutes
a seventh harmonic wave generating optical element is used as the
nonlinear optical crystal 39. A CLBO crystal that constitutes an eighth
harmonic wave generating optical element is used as the nonlinear optical
crystal 40.

[0032] In FIG. 2, elements indicated by elliptical shapes are collimator
lenses, condenser lenses, and the like, and explanations thereof are
omitted. In addition, in FIG. 2, P polarized lights are indicated by
arrows, and S polarized lights are indicated by a dot in a circle;
furthermore, the fundamental wave is denoted as ω and the nth
harmonic wave is denoted as nω.

[0033] As shown in FIG. 2, the fundamental wave of the P polarized light
amplified by the first EDFA 22 enters the nonlinear optical crystal 31
(i.e., a second harmonic wave generating optical element), and what
emerges from the nonlinear optical crystal 31 is the second harmonic wave
of the P polarized light, along with the fundamental wave. The
fundamental wave and the second harmonic wave enter the nonlinear optical
crystal 32 (i.e., a third harmonic wave generating optical element). What
emerges from the nonlinear optical crystal 32 is the third harmonic wave
of the S polarized light, along with the fundamental wave and the second
harmonic wave.

[0034] These lights pass through a double wavelength waveplate 33, and
thereby only the second harmonic wave is converted to S polarized light.
As the double wavelength waveplate 33, for example, a waveplate is used
that consists of a uniaxial crystalline flat plate that is cut parallel
to the optical axis of the crystal. The waveplate (i.e., the crystal) is
cut such that its thickness is an integer multiple of λ/2 with
respect to the light of one wavelength (i.e., the second harmonic wave)
and is an integer multiple of λ with respect to the light of
another wavelength such that the polarization of the light of the one
wavelength is rotated and the polarization of the light of the other
wavelength is not rotated. Furthermore, the second harmonic wave and the
third harmonic wave, both of which have become S polarized lights, enter
the nonlinear optical crystal 34 (i.e., a fifth harmonic wave generating
optical element). What emerges from the nonlinear optical crystal 34 is
the fifth harmonic wave of the P polarized light, along with the second
harmonic wave and the third harmonic wave. Furthermore, the fundamental
wave of the P polarized light transmits through the nonlinear optical
crystal 34 as is.

[0035] Because of the effects of walk-off, the cross section of the fifth
harmonic wave generated by the nonlinear optical crystal 34 has an
elliptical shape that, if left as is, will degrade convergence and cannot
be used in the next wavelength conversion. Accordingly, cylindrical
lenses 35, 36 shape the cross section from the elliptical shape into a
circular shape.

[0036] Moreover, the fundamental wave of the P polarized light amplified
by the second EDFA 24 enters the nonlinear optical crystal 37 (i.e., a
second harmonic wave generating optical element), and what emerges from
the nonlinear optical crystal 37 is the second harmonic wave of the P
polarized light, along with the fundamental wave.

[0037] Furthermore, the fundamental wave of the S polarized light
amplified by the third EDFA 26 is combined by a dichroic mirror 41 with
the second harmonic wave of the P polarized light discussed above. In
this example, the dichroic mirror 41 transmits the fundamental wave and
reflects the second harmonic wave. The combined fundamental wave of the S
polarized light and second harmonic wave of the P polarized light is
further combined with the fifth harmonic wave of the P polarized light
discussed above by a dichroic mirror 38. In this example, the dichroic
mirror 38 transmits the fundamental wave and the second harmonic wave and
reflects the fifth harmonic wave. A bulk optical element can be used for
combining these lights; for example, a color separating and combining
mirror (i.e., a dichroic mirror), a reflective diffractive optical
element, a transmissive diffractive optical element, and the like can be
used.

[0038] The combined fundamental wave of the S polarized light, the second
harmonic wave of the P polarized light, and the fifth harmonic wave of
the P polarized light enters the nonlinear optical crystal 39 (i.e., a
seventh harmonic wave generating optical element), and what emerges from
the nonlinear optical crystal 39 is the seventh harmonic wave of the S
polarized light, along with these lights. These lights enter the
nonlinear optical crystal 40 (i.e., an eighth harmonic wave generating
optical element); here, the fundamental wave of the S polarized light and
the seventh harmonic wave of the S polarized light combine, and the
eighth harmonic wave of the P polarized light is generated. A dichroic
mirror, a polarizing beam splitter, a prism, or the like can be used if
one desires to isolate just the eighth harmonic wave from the lights of
other wavelengths that emerge from the nonlinear optical crystal 40. In
the present embodiment, a dichroic mirror, a polarizing beam splitter, a
prism, or the like (not shown) is used to isolate the eighth harmonic
wave (i.e., light with 1/8 the wavelength of the fundamental wavelength)
from the lights that emerge from the nonlinear optical crystal 40, and
such is output as the output light of the wavelength converting part 30.
In the present embodiment, the output light of the wavelength converting
part 30 serves as the output light of the laser apparatus 1. In the
present embodiment, the output light of the laser apparatus 1 is thereby
ultraviolet pulsed light that is tunable wavelength within a prescribed
range that includes a wavelength equal to 1/8 of 1.547 μm (i.e., 193.4
nm).

[0039] The wavelength of the incident light that impinges each of the
nonlinear optical crystals 31, 32, 34, 37, 39, 40 is determined only by
the fundamental wavelength generated by the fundamental wavelength light
generating unit 10 and is not dependent on the temperatures of the
nonlinear optical crystals 31, 32, 34, 37, 39, 40. Accordingly, the
wavelength of the output light of the wavelength converting part 30 does
not depend on the temperatures of the nonlinear optical crystals 31, 32,
34, 37, 39, 40; furthermore, even if those temperatures vary, the
wavelength output by the wavelength converting part 30 does not change,
namely, it remains 1/8 of the fundamental wavelength generated by the
fundamental wavelength light generating unit 10. However, if the
fundamental wavelength generated by the fundamental wavelength light
generating unit 10 varies in accordance with the output wavelength
instruction signal as discussed above, then the wavelength of the
incident light that accordingly impinges the nonlinear optical crystals
31, 32, 34, 37, 39, 40 varies, as does the wavelength of the output light
of the wavelength converting part 30, and thereby the wavelength
tunability of the output light of the laser apparatus 1 is achieved.

[0040] As shown in FIG. 3, the conversion efficiency of a nonlinear
optical crystal depends not only on the temperature of the nonlinear
optical crystal but also on the wavelength of the incident light that
impinges the nonlinear optical crystal. FIG. 3 is a graph that
schematically shows the temperature dependency of the conversion
efficiency of the nonlinear optical crystal for wavelengths λ1,
λ2, λ3 of the incident light. In the example shown in FIG. 3,
the conversion rate for the wavelength λ1 is maximal at a
temperature T1, the conversion rate for the wavelength λ2 is
maximal at a temperature T2, and the conversion rate for the wavelength
λ3 is maximal at a temperature T3.

[0041] Accordingly, even if the temperature of each of the nonlinear
optical crystals 31, 32, 34, 37, 39, 40 is set such that the conversion
efficiency of the relevant nonlinear optical crystal 31, 32, 34, 37, 39,
40 is maximal for a certain wavelength of the output light of the laser
apparatus 1 (and, in turn, the fundamental wavelength generated by the
fundamental wavelength light generating unit 10), if we assume that those
temperatures are maintained continuously as is and that the wavelength of
the output light of the laser apparatus 1 (and, in turn, the fundamental
wavelength generated by the fundamental wavelength light generating unit
10) varies, then the wavelength of the light that impinges each of the
nonlinear optical crystals 31, 32, 34, 37, 39, 40 will vary and,
accordingly, the conversion efficiency of the nonlinear optical crystals
31, 32, 34, 37, 39, 40 will decrease. Furthermore, the larger the shift
in that wavelength, the more the conversion efficiency of the nonlinear
optical crystals 31, 32, 34, 37, 39, 40 will decrease, which is a
problem. For example, if the temperature of the nonlinear optical crystal
that has the characteristics shown in FIG. 3 is set to T2 such that the
conversion efficiency is maximal when the incident light has the
wavelength λ2 and that temperature T2 is maintained continuously,
then the wavelength of the incident light will shift from λ2 toward
the λ1 side or toward the λ3 side, thereby reducing the
conversion efficiency of the nonlinear optical crystal; furthermore, the
larger the shift in the wavelength, the greater the decrease in the
conversion efficiency.

[0042] If the conversion efficiency of the nonlinear optical crystals 31,
32, 34, 37, 39, 40 decreases significantly, then the power level of the
output light of the laser apparatus 1 will decrease significantly, making
it unfit for use. Accordingly, even if the temperature of each of the
nonlinear optical crystals 31, 32, 34, 37, 39, 40 is optimized for a
given wavelength of the output light of the laser apparatus 1, the tuning
range of the wavelength of the output light of the laser apparatus 1 will
narrow if those temperatures are maintained continuously, which is a
problem.

[0043] In contrast, in the present embodiment, even if the wavelength of
the output light of the laser apparatus 1 (and, in turn, the fundamental
wavelength generated by the fundamental wavelength light generating unit
10) is varied by the main control unit 50, the correspondence information
storage unit 60, and the temperature control unit 70, that wavelength is
tracked and the temperatures of the nonlinear optical crystals 31, 32,
34, 37, 39, 40 are each controlled such that those temperatures are
optimized with respect to conversion efficiency. Accordingly, the tuning
range of the wavelength of the output light of the laser apparatus 1
according to the present embodiment can be expanded significantly. This
point is discussed in detail below.

[0044] In addition to the correspondence information that indicates the
output wavelength and laser temperature correspondence relationship
discussed above, the correspondence information that indicates the
correspondence relationship between the wavelength of the output light of
the laser apparatus 1 with respect to each of the nonlinear optical
crystals 31, 32, 34, 37, 39, 40, on the one hand, and for each of the
nonlinear optical crystals 31, 32, 34, 37, 39, 40 the temperature at
which the conversion efficiency is maximal or near maximal for the
wavelength of the light that impinges the given nonlinear optical crystal
when the output light of that wavelength is output from the laser
apparatus 1, on the other hand, (hereinbelow, called the "output
wavelength and crystal temperature correspondence relationship") is also
prestored in the correspondence information storage unit 60. For example,
for a nonlinear optical crystal that has the characteristics shown in
FIG. 3, if incident lights at the wavelengths λ1, λ2,
λ3, which correspond to first through third wavelengths of the
output light of the laser apparatus 1, impinge the relevant nonlinear
optical crystal, then correspondence information that indicates that the
first through third wavelengths correspond to the temperatures T1, T2,
T3, respectively, is stored in the correspondence information storage
unit 60 as the correspondence information that indicates the output
wavelength and crystal temperature correspondence relationship of the
relevant nonlinear optical crystal. There are individual differences in
the correspondence relationship between the wavelength of the incident
light of the nonlinear optical crystal and the temperature at which the
conversion efficiency is maximal. Consequently, it is preferable to
obtain the output wavelength and crystal temperature correspondence
relationship, in advance, based on the result of actually measuring the
temperature detected by the temperature detector 11b and actually
measuring the conversion efficiency while successively varying the
temperature regulation state of the temperature regulator 11a as the
wavelength of the incident light on each of the nonlinear optical
crystals 31, 32, 34, 37, 39, 40 is successively varied. The
correspondence information that indicates the output wavelength and
crystal temperature correspondence relationship may be stored in the
correspondence information storage unit 60 in the form of, for example,
an approximation expression or a lookup table.

[0045] When controlling the temperatures of the nonlinear optical crystals
31, 32, 34, 37, 39, 40, the main control unit 50 references the
correspondence information stored in the correspondence information
storage unit 60 based on the output wavelength instruction signal in
order to acquire the temperatures of the nonlinear optical crystals 31,
32, 34, 37, 39, 40 to be set in accordance with the output wavelength
indicated by the output wavelength instruction signal, and supplies those
temperatures to the temperature control unit 70 as the target
temperatures of the nonlinear optical crystals 31, 32, 34, 37, 39, 40.
The temperature control unit 70 performs feedback control such that the
temperature of each of the nonlinear optical crystals 31, 32, 34, 37, 39,
40 reaches its target temperature by supplying, for each of the nonlinear
optical crystals 31, 32, 34, 37, 39, 40, an adjustment signal to the
temperature regulators 31a, 32a, 34a, 37a, 39a, 40a in accordance with
the corresponding target temperature as well as in accordance with the
detection signal output from the corresponding temperature detector 31b,
32b, 34b, 37b, 39b, 40b.

[0046] Accordingly, even if the wavelength of the output light of the
laser apparatus 1 (and, in turn, the fundamental wavelength of the light
output by the fundamental wavelength light generating unit 10) according
to the present embodiment varies, that wavelength is tracked and the
temperatures of the nonlinear optical crystals 31, 32, 34, 37, 39, 40 are
each optimized with respect to conversion efficiency. Consequently, the
tuning range of the wavelength of the output light of the laser apparatus
1 according to the present embodiment can be expanded. Thereby, according
to the present embodiment, a sufficient wavelength tuning performance can
be achieved.

Second Embodiment

[0047]FIG. 4 is a schematic block diagram that shows a light therapy
apparatus 80 according to a second embodiment of the present invention.
FIG. 5 is a schematic block diagram that shows a radiation optical system
100 and an observation optical system 110, which constitute the light
therapy apparatus 80 shown in FIG. 4. The light therapy apparatus 80
according to the present embodiment is an apparatus that comprises and
uses the laser apparatus 1 according to the first embodiment to correct
cornea curvature or irregularity in order to treat myopia, astigmatism,
and the like by radiating ultraviolet laser light (i.e., the output light
of the laser apparatus 1) to a cornea and ablating either the corneal
surface (i.e., in PRK; photorefractive keratectomy) or the interior of an
incised cornea (i.e., in LASIK; laser intrastromal keratomileusis).

[0048] As shown in FIG. 4, the light therapy apparatus 80 basically
comprises, inside an apparatus casing 90, the laser apparatus 1 discussed
above; the radiation optical system 100, which guides and radiates
ultraviolet laser light Lv output from the laser apparatus 1 to a surface
(i.e., a therapy region) of a cornea HC of an eyeball EY; and the
observation optical system 110, which observes the therapy region.

[0049] The apparatus casing 90 is provided and disposed on a base part 91
with an XY motion table 92 interposed therebetween; furthermore, the
entire apparatus casing 90 is configured moveably with respect to the
eyeball EY in the arrow X directions in FIG. 4, namely, in the lateral
directions in the drawing, as well as in the Y directions perpendicular
to the paper surface.

[0050]FIG. 5 shows the configuration of the radiation optical system 100
and the observation optical system 110. The radiation optical system 100
comprises: a condenser lens 101, which condenses the ultraviolet laser
light Lv emitted from the laser apparatus 1 such that it forms a
prescribed spot diameter on the eyeball EY; and a dichroic mirror 102,
which reflects the ultraviolet laser light Lv from the condenser lens 101
and radiates such to the surface of the cornea HC of the eyeball EY,
namely, the therapy target. The dichroic mirror 102 is set such that it
reflects light in the ultraviolet region and transmits light in the
visible region; furthermore, the dichroic mirror 102 can reflect the
ultraviolet laser light Lv coaxially with the optical axis of the
observation optical system 110 and can radiate such to the surface of the
cornea HC as discussed later.

[0051] Moreover, the observation optical system 110 comprises:
illumination lamps 115 that illuminate the surface of the cornea HC of
the eyeball EY, which constitutes the therapy target; an objective 111,
which receives light in the visible region that was radiated by the
illumination lamps 115, reflected by the cornea HC, and transmitted
through the dichroic mirror 102; a prism 112, which reflects the light
from the objective 111; and an eyepiece 113, which receives the reflected
light from the prism 112 and forms an image; furthermore, the observation
optical system 110 is configured such that an enlarged image of the
cornea HC from the light that passes through the eyepiece 113 can be
observed.

[0052] Thereby, a specialist, such as an ophthalmologist, can perform
light therapy while visually observing the therapy target via the
observation optical system 110. For example, while the eyeball EY is
being visually observed, the apparatus casing 90 is moved in the X
directions and the Y directions, the ultraviolet laser light Lv is
radiated as a spot light to the surface of the cornea HC, which is the
therapy target, and thereby the radiated area is ablated. In addition,
corrective therapy, such as the correction of myopia, astigmatism, and
farsightedness, can be performed by using an operation control apparatus
(not shown) to control the operation of the XY motion table 92, moving
the apparatus casing 90 in the X directions and the Y directions,
scanning the surface of the cornea HC with the radiated spot light, and
thereby ablating the corneal surface.

[0053] In the light therapy apparatus of the present embodiment, the laser
apparatus 1 according to the first embodiment is used, and therefore,
even if individual differences arise in the manufacture of the radiation
optical system 100, those individual differences can be compensated for
by varying the wavelength of the output light of the laser apparatus 1.
Furthermore, because the laser apparatus 1 according to the first
embodiment is used, the wavelength of the output light of the laser
apparatus 1 can be varied over a wide range, which makes it possible to
sufficiently compensate for the individual differences even if the
individual differences are relatively large.

Third Embodiment

[0054]FIG. 6 is a schematic block diagram that schematically shows an
exposure apparatus 120 according to a third embodiment of the present
invention. The exposure apparatus 120 according to the present embodiment
uses the laser apparatus 1 according to the first embodiment and is used
by a photolithographic process, which is one of the semiconductor
manufacturing processes. An exposure apparatus that is used in a
photolithographic process operates on the same principle as that of
photoengraving; namely, a device pattern that is precisely drawn on a
photomask (i.e., a reticle) is optically projected and transferred to a
semiconductor wafer, a glass substrate, and the like, which is coated
with a photoresist.

[0055] The exposure apparatus 120 according to the present embodiment
comprises: the laser apparatus 1 discussed above; a radiation optical
system 121 (i.e., an illumination optical system); a mask support
platform 123, which supports a photomask 122; a projection optical system
124; a mounting platform 126 whereon a semiconductor wafer 125, which is
a photosensitive object and constitutes an exposure target, is mounted
and held; and a drive apparatus 127, which moves the mounting platform
126 horizontally.

[0056] In the exposure apparatus 120, the output light output from the
laser apparatus 1 discussed above enters the radiation optical system
121, which comprises a plurality of lenses, passes therethrough, and then
irradiates the entire surface of the photomask 122, which is supported by
the mask support platform 123. In the present embodiment, the laser
apparatus 1 and the radiation optical system 121 constitute a light
radiating apparatus that irradiates the photomask 122, which is the
target. The light radiated in this manner and that passes through the
photomask 122 contains an image of the device pattern drawn on the
photomask 122, and this light transits the projection optical system 124
and is radiated to a prescribed position of the semiconductor wafer 125,
which is mounted on the mounting platform 126. At this time, the image of
the device pattern of the photomask 122 produced by the projection
optical system 124 is reduced and formed on the semiconductor wafer 125,
thereby exposing the semiconductor wafer 125.

[0057] In the exposure apparatus 120 of the present embodiment, the laser
apparatus 1 according to the first embodiment is used, and therefore,
even if individual differences arise in the manufacture of the projection
optical system 124, those individual differences can be compensated for
by varying the wavelength of the output light of the laser apparatus 1.
Furthermore, because the laser apparatus 1 according to the first
embodiment is used, the wavelength of the output light of the laser
apparatus 1 can be varied over a wide range, which makes it possible to
sufficiently compensate for the individual differences even if the
individual differences are relatively large.

[0058] In the device manufacturing method according to one embodiment of
the present invention, a semiconductor device is manufactured by: a
process that designs the functions and performance of the device; a
process that forms a wafer front silicon material; a lithographic
process, including a process that uses the exposure apparatus 120
according to the third embodiment to expose the semiconductor wafer 125
via the photomask 122; a process that forms a circuit pattern by, for
example, etching; a device assembling process (which includes a dicing
process, a bonding process, and a packaging process); and an inspecting
process. Furthermore, the present invention is not limited to an exposure
apparatus for fabricating semiconductor devices and can also be adapted
to exposure apparatuses for fabricating various other devices.

Fourth Embodiment

[0059]FIG. 7 is a schematic block diagram that shows a mask defect
inspection apparatus 130, which serves as an object inspection apparatus,
according to a fourth embodiment of the present invention. In the mask
defect inspection apparatus 130 according to the present embodiment, a
device pattern, which is precisely drawn on a photomask 132, is optically
projected onto a TDI (time delay and integration) sensor 136, the sensor
image and a prescribed reference image are compared, and any defects in
the pattern are identified based on differences between those images.

[0060] The mask defect inspection apparatus 130 comprises: the laser
apparatus 1 according to the first embodiment; an illumination optical
system 131; a mask support platform 133, which supports the photomask
132; a drive apparatus 134, which moves the mask support platform 133
horizontally; a projection optical system 135; and the TDI sensor 136.

[0061] In the mask defect inspection apparatus 130, the output light
output from the laser apparatus 1 discussed above enters the illumination
optical system 131, which comprises a plurality of lenses, passes
therethrough, and is radiated to a prescribed area of the photomask 132,
which is supported by the mask support platform 133. The light that is
radiated in this manner and that passes through the photomask 132
contains an image of the device pattern drawn on the photomask 132;
furthermore, this light transits the projection optical system 135 and
forms an image at a prescribed position of the TDI sensor 136.
Furthermore, the horizontal movement speed of the mask support platform
133 is synchronized to a transfer clock of the TDI sensor 136.

[0062] In the mask defect inspection apparatus 130 of the present
embodiment, the laser apparatus 1 according to the first embodiment is
used, and therefore, even if individual differences arise in the
manufacture of the projection optical system 135, those individual
differences can be compensated for by varying the wavelength of the
output light of the laser apparatus 1. Furthermore, because the laser
apparatus 1 according to the first embodiment is used, the wavelength of
the output light of the laser apparatus 1 can be varied over a wide
range, which makes it possible to sufficiently compensate for the
individual differences even if the individual differences are relatively
large.

[0063] The text above explained the embodiments of the present invention,
but the present invention is not limited to these embodiments.

[0064] For example, it is obvious that the tuning range of the wavelength
of the light output from the laser apparatus 1 is not limited to a range
that includes 193.4 nm, which is a wavelength equal to 1/8 of 1.547
μm. In addition, the configuration of the wavelength converting part
30 is not limited to the configuration discussed above.

[0065] Furthermore, the second through fourth embodiments were offered
merely as examples of apparatuses that use the laser apparatus 1
according to the present invention, and the laser apparatus 1 according
to the present invention can be adapted to various other apparatuses. In
addition, the second through fourth embodiments discussed above are
examples wherein the wavelength tunability of the laser apparatus 1
according to the first embodiment is used to correct the optical system,
but the application of the laser apparatus 1 according to the present
invention is not limited to such a correction. For example, the laser
apparatus 1 according to the present invention may be used in, for
example, a measuring apparatus that performs various measurements by
radiating light to an object to be measured and analyzing the light
reflected therefrom, or to a measuring apparatus that obtains different
information about an object to be measured by actively varying the
wavelength of the measuring beam; furthermore, the output light of the
laser apparatus 1 may be used as the wavelength tunable measuring beam.